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The LVD detector in Gran Sasso 840 scintillator counters, 1.5 m 3 each, are inserted in modules holding 8 counters each. The modules are grouped and stacked together to form three towers of 35 modules each. The scintillator of ach counter (1.2 tons) is watched from the top by 3 PMTs (15 cm diameter). 29 Piero GaleottiVulcano 2008

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The scintillator stability has been monitored for about 2 years using a 252 Cf n-source and periodically measuring: n-capture efficiency n mean capture time Both do not show any hint of variation or degradation. Other measurements are done on smaller samples by directly measuring transmittance and light yield. n-capture efficiency mean capture time stability survey Piero Galeotti 34 Vulcano 2008